Chronicle News Service/Rex LarsenSmaller crowds: A senior citizens group from Coloma, bound for Alaska, arrives at Gerald R. Ford International Airport's temporary loading area as construction continues on the canopy for the parking facility.

GRAND RAPIDS -- With a wavy, glass-and-steel "grand canopy" representing the Great Lakes, the Gerald R. Ford International Airport's $134 million parking ramp is being built for the future.

More than halfway through construction, though, as workers bolt the last of the canopy trusses into place, airport officials concede the outlook is increasingly uncertain.

Passenger counts, which started falling before the airport's Board of Directors voted last year to build the ramp, continue to drop as airlines merge and cut back, leading some administrators to wonder how long it will take to fill the 4,900-space, four-story ramp.